Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 070237 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 1037 PM EDT WED MAY 6 2015 .SYNOPSIS... LOW PRESSURE SOUTH OF CAPE FEAR MAY BECOME A SUBTROPICAL CYCLONE OVER THE NEXT COUPLE OF DAYS. THE SYSTEM IS EXPECTED TO APPROACH THE COAST OF SOUTH CAROLINA OR SOUTHERN NORTH CAROLINA FRIDAY AND SATURDAY WITH INCREASING CHANCES FOR HEAVY RAIN...GUSTY WINDS... AND DANGEROUS RIP CURRENTS AT THE BEACHES. UNSETTLED WEATHER SHOULD PERSIST INTO EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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AS OF 1030 PM WEDNESDAY...I HAVE MADE SMALL TWEAKS TO TEMPERATURES BASED ON OBSERVED HOURLY TEMP CURVES. PRECIP SHIELD IS ONLY 20 MILES FROM BALD HEAD ISLAND AND MEASURABLE RAIN MAY ONLY BE 4 HOURS AWAY FROM REACHING LAND. 00Z MHX SOUNDING REVEALED CONSIDERABLE DRY AIR IN THE 4000-15000 FT LAYER THAT WILL LIMIT WESTWARD PROGRESS OF THE RAIN AS PREVIOUSLY FORECAST. DISCUSSION FROM 730 PM FOLLOWS... THE LOW SEVERAL HUNDRED MILES SOUTH OF CAPE FEAR HAS CHANGED LITTLE IN ORGANIZATION THIS AFTERNOON. THE LATEST WORD FROM THE HURRICANE CENTER IS STILL FOR A 60 PERCENT CHANCE OF DEVELOPMENT INTO A NAMED SUBTROPICAL STORM OVER THE NEXT FEW DAYS. THE NASA GLOBAL PRECIPITATION MISSION (GPM) SATELLITE OVERFLEW THE SYSTEM EARLY THIS AFTERNOON AND SHOWED RAINFALL ECHOES LARGELY DISLOCATED FROM THE SATELLITE-INFERRED CIRCULATION CENTER. (SEE OUR LATEST FACEBOOK/TWITTER POSTS) THIS DOES NOT BODE WELL FOR RAPID STRENGTHENING...ALTHOUGH THIS COULD CHANGE AS THE SYSTEM REMAINS NEAR THE WARM GULF STREAM CURRENT FOR AT LEAST ANOTHER 36 HOURS. DENSE CIRRUS ALONG THE COAST SHOULD CONTINUE OVERNIGHT AS THE UPPER LOW OFFSHORE MAINTAINS A SOUTHERLY FLOW AT 200-300 MB. MOISTURE AT 700 MB IS REMAINING 50+ MILES OFFSHORE WITH RATHER DRY AIR ACROSS THE EASTERN CAROLINAS AT THIS TIME. AS WINDS THROUGHOUT THIS LEVEL TURN MORE EASTERLY TONIGHT THE LARGE SHIELD OF RAIN VISIBLE ON THE PERIPHERY OF OUR RADAR SHOULD SHIFT WESTWARD. I HAVE SLOWED DOWN THE WESTWARD ADVANCE OF PRECIPITATION FROM PREVIOUS FORECASTS A BIT...WITH CHANCES OF MEASURABLE RAIN BY DAYBREAK 30-50 PERCENT AT THE COAST AND 10 PERCENT OR LESS ALONG I-95. NO SIGNIFICANT CHANGES HAVE BEEN MADE TO LOWS...STILL EXPECTED TO RANGE FROM THE UPPER 50S INLAND TO THE LOWER 60S AT THE COAST.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... AS OF 300 PM WEDNESDAY...A LARGE SWATCH OF SHOWERS AND THUNDERSTORMS OFF THE FLORIDA EAST COAST AND IN THE VICINITY OF THE BAHAMAS HAS BEEN RELUCTANT TO BECOME MUCH MORE ORGANIZED TODAY. THE NATIONAL HURRICANE CENTER CONTINUES TO MONITOR AND MAY SEND A PLANE INTO THE SYSTEM ON THURSDAY TO BETTER EVALUATE ITS STRUCTURE AND INTENSITY. MODELS ARE RATHER CONSISTENT IN SHOWING A VERY SLOW EVOLUTION AS THE SHOWERS AND THUNDERSTORMS CONTINUE TO ADVANCE/ EXPAND FURTHER NORTH ACROSS THE EASTERN CAROLINAS. HAVE INCLUDED LIKELY TO WIDESPREAD CONVECTION FOR MUCH OF THE PERIOD. THE PERSISTENCE OF THE RAINFALL MAY LEAD TO A RISK FOR SIGNIFICANT PONDING AND PERHAPS SOME FLOODING. AT THIS TIME...IT IS DIFFICULT TO PINPOINT WHERE THE HEAVIEST OF RAIN WILL FALL. CERTAINLY THERE WILL BE PLENTY OF VERY HEAVY RAINFALL OFFSHORE. IF DEVELOPING LOW PRESSURE IS ABLE TO DRIFT OR REDEVELOP WESTWARD AND CLOSER TO THE COAST...THEN THE RISK FOR EXCESSIVE RAINFALL WILL MOVE ACROSS THE EASTERN CAROLINAS. AT THIS TIME...RAINFALL AMOUNTS UP TO 1 TO 2 INCHES IS CERTAINLY POSSIBLE WITH AGAIN A POTENTIAL FOR MUCH HIGHER AMOUNTS. THE COASTAL AREAS SHOULD BE PRONE TO THE HIGHER RAINFALL TOTALS. OTHERWISE...GUSTY WINDS ARE EXPECTED WITH THE STRONGEST WINDS NOW EXPECTED ON FRI...UP TO 20 TO 30 MPH AND FROM THE NE. THE SURF ZONE WILL LIKELY BECOME DANGEROUS WITH BUILDING BREAKERS...ROUGH SURF...STRONG RIP CURRENTS AND SIGNIFICANT BEACH EROSION. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... AS OF 300 PM WEDNESDAY...SYSTEM STILL SLOW TO ORGANIZE TODAY OFF THE SOUTHEAST COAST. SO SLOW IN FACT THAT THE RECON HAS BEEN POSTPONED. UNTIL THIS SYSTEM BEGINS TO CONGEAL (AT WHICH TIME AIRCRAFT RECON WILL BECOME LIKELY) ITS STILL VERY TOUGH TO ASCERTAIN HOW THINGS WILL PAN OUT. IN THE VERY NEAR TERM THE SOUTHERN CENTER JUST NORTH OF THE BAHAMAS SEEMS TO BE WEAKENING IN FAVOR OF THE NORTHERN CENTER ROUGHLY EAST OF JACKSONVILLE, FL. THE FORMER IS A WEAK REFLECTION OF THE UPPER LOW WHILE THE LATTER IS THE MORE TYPICAL FRONTAL LOW. MOST MODELS INDICATE THAT THE FRONTAL LOW REMAINS DOMINANT AND THAT THE FRONTAL STRUCTURE WEAKENS AS THE SYSTEM MOVES SLOWLY TO THE NORTH. THIS CONTINUES TO BE SUPPORTED BY THE FLORIDA STATE CYCLONE PHASE DIAGRAMS THAT EVENTUALLY INDICATE A WEAKLY WARM CORE SYMMETRIC SYSTEM. SSTS ARE MARGINAL TO SAY THE LEAST SO A HYBRID SYSTEM APPEARS MORE LIKELY THAN PURELY TROPICAL BUT IN THE END NHC WILL HAVE THAT CALL. LOCALLY THE CHANCE FOR HEAVY RAINFALL SEEMS TO BE GOING UP MORE NOTABLY THAN THE CHANCE FOR ANY MEMORABLE WINDS. ASSUMING AT LEAST SOME WARM RAIN PROCESSES THE TRACK OF THIS SYSTEM (IT WILL BE A VERY SLOW MOVER AND MAY EVEN STALL, LOOP, OR RETROGRADE) WE COULD SEE ANYTHING FROM A BENEFICIALLY VERY WET WEEKEND TO SOME ARRANT FLOODING ISSUES. ANOTHER FACTOR THAT COMPLICATES THE RAINFALL POTENTIAL IS THE SEEMING LIKELIHOOD OF A HYBRID SYSTEM. THE RAINFALL DISTRIBUTION WILL NOT BE VERY SYMMETRICAL ABOUT THE CIRCULATION. RATHER, THERE SHOULD BE A FOCUSED CHANNEL OF SOUTHEASTERLY FLOW WHERE A FAIRLY LOCALIZED BULLSEYE OF HEAVY RAINFALL IS FOCUSED. GIVEN THE AFOREMENTIONED POSSIBILITY OF A STALLED OUT SYSTEM THE POP FORECAST WILL ONLY GRADUALLY DECREASE HEADING INTO EARLY NEXT WEEK. MOISTURE FROM THIS SYSTEM COULD CONCEIVABLY LINGER INTO TUESDAY OR WEDNESDAY AT WHICH TIME A COLD FRONT WILL BE APPROACHING FROM THE NORTHWEST. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... AS OF 00Z...CONFIDENCE IS STILL RATHER LOW...BUT IMPROVING AS THE MODELS ARE STARTING TO GET A BIT MORE IN SYNC. LOW PRESSURE WILL SLOWLY APPROACH THE REGION TOWARD MORNING...WITH SHOWERS AND MVFR CONDITIONS EXPECTED AROUND DAYBREAK ALONG THE COAST. THE GRADIENT WILL TIGHTEN ALSO AROUND DAYBREAK...WITH GUSTS OVER 20 KTS A GOOD BET AFTER 13Z. THE INLAND TERMINALS WILL TAKE A WHILE TO GET ANY PRECIP...PERHAPS BY EARLY AFTERNOON. THE COLUMN OF DEEP MOISTURE WILL REMAIN OVER THE REGION THROUGH THE END OF THE FORECAST PERIOD...WITH INTERMITTENT IFR IN THE HEAVIER PRECIP. EXTENDED OUTLOOK...RAIN/MVFR. TEMPO IFR IN HEAVIER SHOWERS HIGHEST CONFIDENCE COASTAL TERMINALS. BECOMING VFR/SHOWERS SUNDAY. VFR ISOLATED SHOWERS MON. && .MARINE...
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NEAR TERM /THROUGH TONIGHT/... AS OF 1030 PM WEDNESDAY...LOW PRESSURE A FEW HUNDRED MILES SOUTH OF CAPE FEAR IS NOT BECOMING APPRECIABLY BETTER ORGANIZED THIS EVENING...BUT CONTINUES TO HAVE A BETTER THAN A 50-50 CHANCE OF BECOMING A NAMED SUBTROPICAL CYCLONE IN THE NEXT FEW DAYS. REGARDLESS OF ITS DESIGNATION...A LARGE COUNTERCLOCKWISE SWIRL OF WINDS FROM CAPE HATTERAS INTO THE NORTHERN BAHAMAS IS BUILDING SEA HEIGHTS AT A PRETTY GOOD RATE EARLY THIS EVENING. DATA FROM THE FRYING PAN SHOALS BUOY INDICATES SEAS ARE ALREADY 7.2 FEET...WITH 4.5-5 FOOT SEAS SHOWING UP VERY CLOSE TO SHORE AT THE TWO CORMP BUOYS NEAR CAPE FEAR. RADAR SHOWS RAIN OFFSHORE ON THE NORTHERN PERIPHERY OF THE CYCLONE HAS PUSHED UP TO ABOUT 20 MILES FROM CAPE FEAR. RELATIVELY DRY AIR SHOULD IMPEDE THIS RAIN FROM MOVING WESTWARD TOO RAPIDLY...BUT SHOWERS SHOULD BE LIKELY ACROSS MOST OF THE WATERS BY DAYBREAK. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 300 PM WEDNESDAY...SMALL CRAFT ADVISORY FLAGS WILL BE FLYING THROUGH THE PERIOD. HOWEVER...THESE FLAGS MAY BE REPLACED BY A TROPICAL STORM WATCH OR WARNING DURING/BY THURSDAY. IN EITHER CASE...THE SLOW EVOLUTION AND MOVEMENT OF THIS SYSTEM UP THE SOUTHEAST COAST AND ITS EXPANSIVE CONVECTION WILL CHURN UP SEAS AND WE ARE EXPECTING SEAS TO BUILD UP TO 6 TO 10 FT...PERHAPS PEAKING THU NIGHT AND FRI. WIND SPEEDS WILL BE UP TO 20 TO 30 KT WITH HIGHER GUSTS AND THE DIRECTION WILL PRIMARILY BE FROM THE NE AND E THU AND THU NIGHT AND E OR SE FRI AND FRI NIGHT. LONG TERM /SATURDAY THROUGH MONDAY/... AS OF 300 PM WEDNESDAY...WE WILL HAVE ADVISORIES UP ON SATURDAY IF NOT TROPICAL WARNINGS FROM NHC. THE POSSIBLE SLOW AND ERRATIC MOVEMENT OF THE SYSTEM WILL MAKE IT TOUGH TO SAY AT WHAT SPEED CONDITIONS WILL IMPROVE AND AT WHAT TIME SUCH HEADLINES CAN BE STEPPED DOWN. A STALLING OF THE STORM COULD ALSO MEAN THAT THE WIND DIRECTION FORECAST IS OFF. IN THE END UNTIL THIS SYSTEM STARTS TO CONGEAL INTO A MORE ORGANIZED AREA OF LOW PRESSURE (TOMORROW OR FRIDAY) THERE IS JUST TOO MUCH UNCERTAINTY TO CHANGE THE FORECAST MUCH AT ALL AT THIS TIME.
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&& .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT FRIDAY FOR AMZ250-252-254- 256. && $$ SYNOPSIS...TRA NEAR TERM...TRA SHORT TERM...RJD LONG TERM...MBB AVIATION...HDL

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